DWI Time of Driving vs. Time of Test

Let Our Houston DWI Lawyers Assist You

An essential element of the crime of
DWI is that the person is intoxicated at the time of driving. However,
chemical tests only reflect a person’s alcohol concentration at the time of testing.
A person’s alcohol concentration at the time of driving may have
been higher, lower or the same.

In order to link the test result to alcohol concentration at the time of
driving the prosecution may attempt to present expert testimony concerning
alcohol concentration at the time of driving. The process the expert uses
to relate the test result back to the time of driving is known as retrograde
extrapolation. However, in order for the expert to offer an opinion which
will be admissible at trial, the court must find that the expert’s
opinion will be reliable.

Factors effecting reliability include:

The length of time between the offense and the test(s) administered;

The number of tests given and the length of time between each test; and

Whether, and if so, to what extent, any individual characteristics of the
defendant were known to the expert.

These characteristics and behaviors might include, but are not limited to:

Weight and gender

Typical drinking pattern

Tolerance for alcohol

How much the person had to drink on the day or night in question,

What the person drank,

The duration of the drinking spree

The time of the last drink, and

How much and what the person had to eat either before, during, or after
the drinking.

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